feat(agent): two-stage memory system with Dream consolidation

Replace single-stage MemoryConsolidator with a two-stage architecture:

- Consolidator: lightweight token-budget triggered summarization,
  appends to HISTORY.md with cursor-based tracking
- Dream: cron-scheduled two-phase processor that analyzes HISTORY.md
  and updates SOUL.md, USER.md, MEMORY.md via AgentRunner with
  edit_file tools for surgical, fault-tolerant updates

New files: MemoryStore (pure file I/O), Dream class, DreamConfig,
/dream and /dream-log commands. 89 tests covering all components.

tests/agent/test_memory_store.py

@@ -0,0 +1,133 @@
+"""Tests for the restructured MemoryStore — pure file I/O layer."""
+
+import json
+
+import pytest
+from pathlib import Path
+
+from nanobot.agent.memory import MemoryStore
+
+
+@pytest.fixture
+def store(tmp_path):
+    return MemoryStore(tmp_path)
+
+
+class TestMemoryStoreBasicIO:
+    def test_read_memory_returns_empty_when_missing(self, store):
+        assert store.read_memory() == ""
+
+    def test_write_and_read_memory(self, store):
+        store.write_memory("hello")
+        assert store.read_memory() == "hello"
+
+    def test_read_soul_returns_empty_when_missing(self, store):
+        assert store.read_soul() == ""
+
+    def test_write_and_read_soul(self, store):
+        store.write_soul("soul content")
+        assert store.read_soul() == "soul content"
+
+    def test_read_user_returns_empty_when_missing(self, store):
+        assert store.read_user() == ""
+
+    def test_write_and_read_user(self, store):
+        store.write_user("user content")
+        assert store.read_user() == "user content"
+
+    def test_get_memory_context_returns_empty_when_missing(self, store):
+        assert store.get_memory_context() == ""
+
+    def test_get_memory_context_returns_formatted_content(self, store):
+        store.write_memory("important fact")
+        ctx = store.get_memory_context()
+        assert "Long-term Memory" in ctx
+        assert "important fact" in ctx
+
+
+class TestHistoryWithCursor:
+    def test_append_history_returns_cursor(self, store):
+        cursor = store.append_history("event 1")
+        assert cursor == 1
+        cursor2 = store.append_history("event 2")
+        assert cursor2 == 2
+
+    def test_append_history_includes_cursor_in_file(self, store):
+        store.append_history("event 1")
+        content = store.read_file(store.history_file)
+        data = json.loads(content)
+        assert data["cursor"] == 1
+
+    def test_cursor_persists_across_appends(self, store):
+        store.append_history("event 1")
+        store.append_history("event 2")
+        cursor = store.append_history("event 3")
+        assert cursor == 3
+
+    def test_read_unprocessed_history(self, store):
+        store.append_history("event 1")
+        store.append_history("event 2")
+        store.append_history("event 3")
+        entries = store.read_unprocessed_history(since_cursor=1)
+        assert len(entries) == 2
+        assert entries[0]["cursor"] == 2
+
+    def test_read_unprocessed_history_returns_all_when_cursor_zero(self, store):
+        store.append_history("event 1")
+        store.append_history("event 2")
+        entries = store.read_unprocessed_history(since_cursor=0)
+        assert len(entries) == 2
+
+    def test_compact_history_drops_oldest(self, tmp_path):
+        store = MemoryStore(tmp_path, max_history_entries=2)
+        store.append_history("event 1")
+        store.append_history("event 2")
+        store.append_history("event 3")
+        store.append_history("event 4")
+        store.append_history("event 5")
+        store.compact_history()
+        entries = store.read_unprocessed_history(since_cursor=0)
+        assert len(entries) == 2
+        assert entries[0]["cursor"] in {4, 5}
+
+
+class TestDreamCursor:
+    def test_initial_cursor_is_zero(self, store):
+        assert store.get_last_dream_cursor() == 0
+
+    def test_set_and_get_cursor(self, store):
+        store.set_last_dream_cursor(5)
+        assert store.get_last_dream_cursor() == 5
+
+    def test_cursor_persists(self, store):
+        store.set_last_dream_cursor(3)
+        store2 = MemoryStore(store.workspace)
+        assert store2.get_last_dream_cursor() == 3
+
+
+class TestDreamLog:
+    def test_read_dream_log_returns_empty_when_missing(self, store):
+        assert store.read_dream_log() == ""
+
+    def test_append_dream_log(self, store):
+        store.append_dream_log("## 2026-03-30\nProcessed entries #1-#5")
+        log = store.read_dream_log()
+        assert "Processed entries #1-#5" in log
+
+    def test_append_dream_log_is_additive(self, store):
+        store.append_dream_log("first run")
+        store.append_dream_log("second run")
+        log = store.read_dream_log()
+        assert "first run" in log
+        assert "second run" in log
+
+
+class TestLegacyHistoryMigration:
+    def test_read_unprocessed_history_handles_entries_without_cursor(self, store):
+        """JSONL entries with cursor=1 are correctly parsed and returned."""
+        store.history_file.write_text(
+            '{"cursor": 1, "timestamp": "2026-03-30 14:30", "content": "Old event"}\n',
+            encoding="utf-8")
+        entries = store.read_unprocessed_history(since_cursor=0)
+        assert len(entries) == 1
+        assert entries[0]["cursor"] == 1